82 928 mpg help

[spooledx2]

Hey gents,

I am a 928 junky. Through the years my dad has had quite a few... 89 S4, 87 S4, 1980, and now my old 86S. I have a few as well... an 82 S with 105k, a 1980 5 spd and a 79 no sunroof car.

The 82 has been sitting under cover for about 10 yrs just awaiting resurrection which I am in the process of doing now. The car is primo with a few exceptions and only has 106,000 on it.

The last two tanks I have gotten about 10 mpg(or less) on and anytime you step on it there is a huge cloud of unburnt fuel that spews out the back. I have run some Lucas through it as well as replaced the injector seals(some of them were leaking) and had the injectors tested while I had them out. They tested out great. I also replaced all the vacuum lines while I was in there most of which shattered into a million pieces as soon as I touched them. I have swapped MAF's just to see if it was bad but still having the same issues. I have changed out the cold start injector and I am getting ready to install a new o2 sensor as well...Before I go testing all the sensors or just randomly replacing stuff, is there anything that springs to mind in any of you that might be the issue, or has anyone had the same issues?

Thanks for your time.

Ramon

[MPDano]

82 US or Euro?

[spooledx2]

82 US. sorry that would be helpful info lol

[MPDano]

I think your on the right path.

Did you replace all the Fuel Filters? Did you drop that 10 year old gas out and clean the tank prior to starting?

Replace that O2 and then report back. This may be the fix.

[spooledx2]

I did drain the tank and flush it out... I have put a few thousand miles on it since while messing with it. So all the remainder should have been long gone. I will have it in tonight when I put the test pipe on. Hopefully that takes care of it.

Thanks Dano.

Ramon

[MPDano]

Also, disconnect your battery before you install the O2 Sensor so your Computer can relearn again. After O2 install, then reconnect battery. I'm not sure how much time it needs to be disconnected. Probably not long since I don't believe there is any sort of internal batteries in the L-Jet.

I'm sure I'll get corrected on this as I am also new to Electronic FI, but it worked for me.

Anyways, report back after.

[spooledx2]

Ok so I swapped out the o2 sensor, when i replaced the cats with test pipes...... Man it woke this car up. But still the gas consumption remains the same. Looks like I will be getting about 120 miles out of this tankful. Granted 10 miles of that my foot was through the floor boards pushing on the back of the engine in frustration... but still this is crazy..

I am open to any ideas or suggestions, before I take it into the shop and have someone look into it.

Thanks gents

[Dean_Fuller]

Wild guess but have you checked voltage to the fuel pump? Is it the correct fuel pump?

[JhwShark]

Are you burning low octane, if not try a tank...lower flash point burns more of the fuel...could help a bit.

[joejoe1]

My '81 had a similar problem. What I found was the vacuum advance/retard unit inside the distributor had fallen off. The PO did not realize this and had pulled distributor and advanced it 1 or 2 teeth (I do not remember now) along with turning full advance with adjustment when reinstalled. The car ran like a raped ape, but could not get better than 11 mpg. It did pass California smog twice this way however.

I pulled and reoriented distributor and reattached vac advance unit re-timed car and achieved much better mpg (17-20 town, 27+ on long trips)

[Maleficio]

Is your coil in good shape? I replaced mine with a Jacob's unit. Very nice.

I have an 82 auto. I can never get better than 15.

Good luck, and please report back with your findings.

[spooledx2]

Gents,

So this last weekend I tore back into the beast and here is what I found.

First I took JhwShark's advice and ran a tank of low grade Chevron fuel through it. I didnt notice much of a change but I did notice that she didn't spew quite as much fuel at idle.

The next thing I did was look into what joejoe1 was talking about and yanked the distributor to clean it up and have a look. The main power lead headed back over to the 14 pin connector had about 4 breaks in it. Two of them were through the shielding, and into the main wire so I put some shrink tubing around them and sealed those off. The next thing I found was the cap and rotor were all arc'd out, so I cleaned them up the best I could since no one had a set in stock locally. I put it back together and slapped the dist. back in and fired her up. At first it was still blowing black smoke(I assume burning out all the excess that was in the cylinders). I took her for a run in the foothills and she started to clean out. By the time I got back to the house she was burning nice and clean. I went and filled up the tank and ran it about 150 miles this last weekend.

On the last tank I got 120 miles on a full tank. I am now sitting about 3/8 of a tank on 150(of hard driving) miles so a drastic improvement for sure. I am ordering a new cap and rotor for it and thinking of doing a new coil as well, just to start things off fresh.

So all this time of screwing with the fuel system(which a lot of it was much needed after sitting so long), it looks like the majority of my issues were coming from spark.

I will keep screwing with it to see how much better I can get out of it. I do need to adjust the idle after deleting the cat, its Idling about 1200 in park so I will figure out how to adjust that today and go from there.

Thanks again for all your help and suggestions! You guys are a life/wallet saver. Great site, great people... couldn't ask for more!

Ramon

[MPDano]

I love great news like that. So you must be talking about the Green Wire back to the 14 Pin? Correct? If so, yup a lot of issues can be resolved at this area. Lot's of insulation breaks and corrosion.

[spooledx2]

Yep thats the one. Poor old car is finally getting some much needed love after sitting for so long.

Thanks again gents. The Mistress, thanks you as well.

[Landseer]

Damn. That car IS primo.

[Mrmerlin]

you should also consider getting a new Green wire its a sure bet if you found breaks in the wire it has corrosion inside it and this will reduce the signal to the computer and quite possibly cure the ignition system issues for good

[spooledx2]

Thanks landsheer. She is a 20 footer right now. It was owned by a doctor in Sun Valley, ID whom I purchased it from, very well cared for and a full service history as well.

Mrmerlin. I wondered if one of those could be purchased or not. I would love to have a new one. I will do some searching for sure.

Ramon

[spooledx2]

$133.00! Good lord thats a lot of cheese.... Good investment I am sure... oh well its just money I guess lol.

[spooledx2]

Well that was the most short lived fix in the history of fixes..... Started running like crap again this morning. Going to pull the cap and rotor again tonight and swap them with the new ones. Also going to change out the coil and install the new cold start sensor. The one I swapped it out with was on off of my '80 5spd parts car.

The thing that gets me is when I pulled the cap and rotor they were arc'd out pretty bad. Looked like welding flash on the contact points. Any ideas on wheat could cause this? I should have taken a pic, and if it looks the same tonight I will post up a pic.

Once again thanks for all the help gents.

Ramon

[Mrmerlin]

Ramon the green wire,
the green wire ,
the green wire.
use the old coil and a new cap and rotor,
but put in a new green wire first.
also check the resistors on the fender well for clean connections and correct OHM readings,
if either one of these are not working properly then the ignition will not function as it should . BUT first replace the green wire